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<div class="refentry">
<a name="Domain"></a><div class="titlepage"></div>
<div class="refnamediv">
<h2><span class="refentrytitle">Concept Domain</span></h2>
<p>Domain</p>
</div>
<div class="refsect1">
<a name="id-1.3.32.5.60.3"></a><h2>Description</h2>
<p>
      A Domain creates an association between expressions and a so-called
      generator, which is a function that maps an expression in the default
      domain to an equivalent expression in this Domain. It also associates
      an expression with a grammar, to which all expressions within this
      Domain must conform.
    </p>
</div>
<div class="refsect1">
<a name="id-1.3.32.5.60.4"></a><h2>Associated types</h2>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
<p><span class="bold"><strong>proto_grammar</strong></span></p>
<pre class="literallayout">Domain::proto_grammar</pre>
<p>
      </p>
<p>The grammar to which every expression in this Domain
        must conform.</p>
<p>
    </p>
</li>
<li class="listitem">
<p><span class="bold"><strong>proto_generator</strong></span></p>
<pre class="literallayout">Domain::proto_generator</pre>
<p>
      </p>
<p>
        A Unary Polymorphic Function that accepts expressions in the
        default domain and emits expressions in this Domain.
      </p>
<p>
    </p>
</li>
<li class="listitem">
<p><span class="bold"><strong>proto_super_domain</strong></span></p>
<pre class="literallayout">Domain::proto_super_domain</pre>
<p>
      </p>
<p>
        The Domain that is a super-domain of this domain, if
        any such domain exists. If not, it is some unspecified
        type.
      </p>
<p>
    </p>
</li>
<li class="listitem">
<p><span class="bold"><strong>result_type</strong></span></p>
<pre class="literallayout">boost::result_of&lt;Domain(Expr)&gt;::type</pre>
<p>
      </p>
<p>
        The type of the result of applying
        <code class="computeroutput">proto_generator</code> to
        the specified expression type. The result is required to
        model <a class="link" href="Expr.html" title="Concept Expr">Expr</a>. The domain type
        associated with <code class="computeroutput">result_type</code>
        (<code class="computeroutput">result_type::proto_domain</code>)
        is required to be the same type as this Domain.
      </p>
<p>
    </p>
</li>
<li class="listitem">
<p><span class="bold"><strong>as_expr_result_type</strong></span></p>
<pre class="literallayout">Domain::as_expr&lt;Object&gt;::result_type</pre>
<p>
      </p>
<p>
        The result of converting some type to a Proto expression
        type in this domain. This is used, for instance, when
        calculating the type of a variable to hold a Proto
        expression.
        <code class="computeroutput">as_expr_result_type</code>
        models
        <code class="computeroutput"><a class="link" href="Expr.html" title="Concept Expr">Expr</a></code>.
      </p>
<p>
    </p>
</li>
<li class="listitem">
<p><span class="bold"><strong>as_child_result_type</strong></span></p>
<pre class="literallayout">Domain::as_child&lt;Object&gt;::result_type</pre>
<p>
      </p>
<p>
        The result of converting some type to a Proto expression
        type in this domain. This is used, for instance, to
        compute the type of an object suitable for storage
        as a child in an expression tree.
        <code class="computeroutput">as_child_result_type</code>
        models
        <code class="computeroutput"><a class="link" href="Expr.html" title="Concept Expr">Expr</a></code>.
      </p>
<p>
    </p>
</li>
</ul></div>
</div>
<div class="refsect1">
<a name="id-1.3.32.5.60.5"></a><h2>Notation</h2>
<div class="variablelist"><dl class="variablelist">
<dt><span class="term">Domain</span></dt>
<dd>A type playing the role of domain-type in the <a class="link" href="Domain.html" title="Concept Domain">Domain</a> concept.</dd>
<dt><span class="term">Expr</span></dt>
<dd>A type playing the role of expression-type in the <a class="link" href="Domain.html" title="Concept Domain">Domain</a> concept.</dd>
<dt><span class="term">Object</span></dt>
<dd>A type playing the role of object-type in the <a class="link" href="Domain.html" title="Concept Domain">Domain</a> concept.</dd>
<dt><span class="term"><code class="varname">d</code></span></dt>
<dd>Object of type Domain</dd>
<dt><span class="term"><code class="varname">e</code></span></dt>
<dd>Object of type Expr</dd>
<dt><span class="term"><code class="varname">o</code></span></dt>
<dd>Object of type Object</dd>
</dl></div>
</div>
<div class="refsect1">
<a name="id-1.3.32.5.60.6"></a><h2>Valid expressions</h2>
<div class="informaltable"><table class="table">
<colgroup>
<col>
<col>
<col>
<col>
</colgroup>
<thead><tr>
<th>Name</th>
<th>Expression</th>
<th>Type</th>
<th>Semantics</th>
</tr></thead>
<tbody>
<tr>
<td><p>Apply Generator</p></td>
<td><p>d(e)</p></td>
<td><p><span class="type">result_type</span></p></td>
<td><p>
      The result of applying <code class="computeroutput">proto_generator</code>
      to the specified expression.
    </p></td>
</tr>
<tr>
<td><p>As Expression</p></td>
<td><p>Domain::as_expr&lt; Object &gt;()(o)</p></td>
<td><p><span class="type">as_expr_result_type</span></p></td>
<td><p>
      The result of converting some object to a Proto expression
      in this domain. It returns a Proto expression object that
      is suitable for storage in a variable. It should return a
      new object, which may be a copy of the object passed in.
    </p></td>
</tr>
<tr>
<td><p>As Child</p></td>
<td><p>Domain::as_child&lt; Object &gt;()(o)</p></td>
<td><p><span class="type">as_child_result_type</span></p></td>
<td><p>
      The result of converting some object to a Proto expression
      in this domain. It returns an object suitable for storage
      as a child in an expression tree, which may simply be a
      reference to the object passed in.
    </p></td>
</tr>
</tbody>
</table></div>
</div>
<div class="refsect1">
<a name="id-1.3.32.5.60.7"></a><h2>Models</h2>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><span class="simplelist"><span class="type">boost::proto::default_domain</span></span></li></ul></div>
</div>
</div>
<div class="copyright-footer">Copyright © 2008 Eric Niebler<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
      </p>
</div>
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